The figure is armed with the same carbine he's standing on.
I got interested in the XM177E2 during the playtest for GURPS: SEAL's in Vietnam. The figure is of the character I generated for the playtest. The actual gun was inspired by character.
That there is a fully registered short barrel rifle. Sabrina is a 95% clone of an XM177E2. The 11.5" barrel and mock-moderator is just barely shorter than a 14.5" barrel and normal flash-hider. Lots of retro-heads use a 12.7" barrel and pin and weld the moderator on to make a Title 1 version; it's actually a very subtle difference.